1. Field of the Invention
The present invention relates to an electromagnetic forming device for a sheet of material. More particularly, the present invention relates to an electromagnetic forming device for a sheet of material including a magnetic concentration block.
2. Description of the Related Art
FIG. 1 shows a schematic cross-sectional view of a conventional electromagnetic forming device for a sheet of material as disclosed in U.S. Pat. No. 7,069,756. The conventional electromagnetic forming device 1 includes a conductive frame 11, an electromagnetic actuator 12, and a die portion 13. The die portion 13 defines a profiled die surface 132. The electromagnetic actuator 12 is arranged opposite the profiled die surface 132 of the die portion 13, and comprises a plurality of turns of inductive coils (not shown). A sheet of material 14 is secured in a position between the electromagnetic actuator 12 and the profiled die surface 132.
The operation manner of the electromagnetic forming device 1 is as follows. First, a clamp device (not shown) is used to apply a clamping force 17 on the conductive frame 11 and the die portion 13, so as to clamp the sheet of material 14. Then, the electromagnetic actuator 12 are powered to generate an impulse current 15 therein. Meanwhile, the conductive frame 11 and the sheet of material 14 are induced to generate an eddy current 16. As the impulse current 15 and the eddy current 16 are in opposite directions, the magnetic fields generated are also in opposite directions, so a repulsive force is generated between the electromagnetic actuator 12 and the sheet of material 14. Therefore, the sheet of material 14 impacts the profiled die surface 132 of the die portion 13 at a high speed, and has a pattern corresponding to the profiled die surface 132.
The disadvantages of the electromagnetic forming device 1 are as follows. Among the plurality of turns of inductive coils, as a gap exists between neighboring coils, the magnetic field in the space close to the coils is not uniformly distributed. Therefore, when the electromagnetic forming device 1 is used to form workpieces with fine structural patterns, the fine structural patterns may become partially vague where the magnetic fields are weak. In addition, in order to process products with different shapes or patterns, different forms of electromagnetic actuator 12 must be used, so the processing cost will increase.
Therefore, it is necessary to provide an electromagnetic forming device for a sheet of material to solve the above problems.